Alcoholism is a chronic relapsing disorder associated with excessive consumption after periods of abstinence. Neuroadaptations in brain structure, plasticity and gene expression occur with chronic intoxication but are poorly characterized in abstinence. We propose that the identification of pathways altered during abstinence in prefrontal cortex, a brain region associated with cognitive dysfunction and damage in alcoholics, will provide information relevant to the risk of relapse in both sexes. To evaluate the influence of genetic differences, animal models with widely divergent responses to alcohol withdrawal are employed, including the Withdrawal Seizure-Resistant (WSR) and Withdrawal Seizure-Prone (WSP) selected lines. To focus results for phenotype- specific analysis of expression differences, a second model with divergent withdrawal responses, strains of inbred C57BL/6J vs. DBA/2J mice, will also be employed. Male and female mice are chronically exposed to highly intoxicating concentrations of ethanol and withdrawn, then left abstinent for 21 days. A systematic approach will be taken to characterize significant expression differences important in mediating risk of relapse, with three specific aims. Specific aim 1 will employ high density cDNA transcriptional profiling and bioinformatic analyses to identify novel pathways significantly altered during abstinence that is dependent on withdrawal response phenotype. The second aim will functionally test the ability of identified pathways to influence relapse, using a withdrawal-induced relapse model of elevated relapse drinking for behavioral validation of expression differences. The third aim will define the neurotoxic and neuroadaptive consequences of persistent expression differences in these low and high withdrawal response models, and whether successful reductions in relapse drinking also reduces active neurotoxicity. Our results indicate a fundamentally distinct neuroadaptive response during abstinence in mice genetically selected for divergent withdrawal severity, with increased risk of relapse in animals with a low withdrawal response to alcohol. Identification of pathways altered in abstinence in both sexes will provide clinically relevant toos to aid development of novel therapeutics for targeted treatment of relapse in a subset of abstinent alcoholics.